possibly fix bug while persing identifiers for [!list]

RELEASENOTE.md

@@ -1,6 +1,10 @@
-Version Notes (Current Version: v2.56.7)
+Version Notes (Current Version: v2.56.8)
 =======================================
 
+v.2.56.8
+-----------
+1. Fix a bug where dot (`.`) wouldn't be considered as identifier in `[!list]` parsing
+
 v.2.56.7
 -----------
 1. Fix parsing for [!list] - more attributes are parsed correctly without quotation

src/Microsoft.DocAsCode.Build.ConceptualDocuments/ListOperatorHelpers/ListOperatorParser.cs

@@ -173,13 +173,14 @@ static bool ContinueParsing(this Context? ctx, ref Context pos)
             for (int i = ctx.Index; next?.Overflow == false; i++)
             {
                 // identifier is anything starting with letter, then followed
-                // by digit, underscore (_) or dash(-)
+                // by digit, underscore (_) or dash(-) or dot (.)
                 // allow starting symbol to be digit, so that we can have numbers
                 if (char.IsLetterOrDigit(next.Value.Symbol) ||
                     (i > ctx.Index && 
                         (
                             (next.Value.Symbol == '_')
                             || (next.Value.Symbol == '-')
+                            || (next.Value.Symbol == '.')
                         )
                     )
                 )